The present invention relates to a heater supporting structure and a heating furnace for bending a glass sheet, in particular to a heater supporting structure and a heating furnace for bending a glass sheet, which are suited to bend a glass sheet for laminated glass to be used for the windshield of an automobile.
The windshield of an automobile is prepared by putting a glass sheet cut in certain size and shape on a mold and heating the glass sheet to a temperature close to a softening point (550xc2x0 C.-650xc2x0 C.) in a heating furnace to be bent in a certain shape.
The heating furnace for heating the glass sheet has an inner space divided into a plurality of zones, and the respective zones are provided with heaters segmented into a plurality of blocks. The respective heaters are independently subjected to temperature control and are controlled to provide certain temperature distributions in the respective blocks. The glass sheet is heated by the segmented heaters to have temperature distributions formed in a glass surface, being bent into the certain shape.
By the way, conventional ceiling heaters, which are provided on the ceiling surfaces of the respective zones in the heating furnace, are configured by providing a plurality of cylindrical heating elements on supporting frames side by side.
However, the ceiling heaters, which are conventionally configured by providing cylindrical heating elements side by side, have created a problem in that the stay of heat causes the heat to be easily transferred among the respective heating elements, and clear temperature distributions are difficult to be formed.
It is object of the present invention to solve this problem and to provide a heater supporting structure superior in temperature control and a heating furnace for bending a glass sheet capable of improving temperature distribution generating properties therein.
The present invention provides a heater supporting structure including heaters comprising plate-shaped electrical resistance heating elements and power applying portions for energizing the electrical resistance heating elements, mounts for mounting the electrical resistance heating elements, and first insulative supporters and second insulative supporters, the supporters being provided on the mounts with a certain distance and supporting edges of the electrical resistance heating elements, characterized in that the electrical resistance heating elements are formed in a shape so as to project toward the mounts and are provided apart from the mounts.
The present invention also provides the following modes. Specifically, there is provided the heater supporting structure, wherein a first supporter, a second supporter and an electrical resistance heating element form one unit, and a plurality units are provided so as to be side by side. Additionally, there is provided the heater supporting structure, wherein two adjacent electrical resistance heating elements are commonly supported by a supporter, and the plurality of units are delimited by the supporters. Additionally, there is provided the heater supporting structure as defined earlier, wherein the electrical resistance heating elements have elasticity, and the edges of the electrical resistance heating elements are supported by the first and second supporters by repulsive force caused by curvature. Further, there is provided the heater supporting structure as defined earlier, wherein each of the electrical resistance heating elements is made of a metallic sheet having a plurality of slits provided with certain intervals therein to provide a snaky resistance wire.
Furthermore, there is provided a heating furnace for bending a glass sheet, wherein a mold for having a glass sheet put thereon is provided, and the glass sheet is heated by a heating device to be bent in a certain shape, characterized in that the heating device includes the heater supporting structure as stated earlier.